Catheters are used in various interventional procedures for delivering therapeutic means to a treated site (e.g., body organ or passageway such as blood vessels). In many cases, a catheter with a small distal inflatable balloon is guided to the treated site. Once the balloon is in place it is inflated by the operator for affixing it in place, for expanding a blocked vessel, for placing treatment means (e.g., stent) and/or for delivering surgical tools (e.g. knives, drills etc.) to a desired site. In addition, catheter systems have also been designed and used for retrieval of objects such as stents from body passageways.
Two basic types of catheter have been developed for intravascular use: over-the-wire (OTW) catheters and rapid-exchange catheters.
OTW catheter systems are characterized by the presence of a full-length guide wire, such that when the catheter is in its in situ working position, said guide wire passes through the entire length of a lumen formed in, or externally attached to, the catheter. OTW systems have several operational advantages which are related to the use of a full length guide wire, including good stiffness and pushability, features which are important when maneuvering balloon catheters along tortuous and/or partially occluded blood vessels.
U.S. Pat. No. 6,039,721 to Johnson et al., describes a balloon catheter system comprising two concentrically-arranged conduits, with a balloon connected between the distal regions thereof. The catheter system permits both expansion/deflation of the balloon and alteration in the length of the balloon when in situ, such that the balloon may be moved between extended and intussuscepted conformations. The catheter system is constructed in order that it may be used for two main purposes: firstly, treatment (i.e. expansion) of different-length stenosed portions of blood vessels with a single balloon and secondly, the delivery of either stents or medication to intravascular lesions, wherein the stent or medication is contained within the distally-intussuscepted portion of the balloon. When used for multiple, differing-length lesion expansion, the balloon is inserted into a blood vessel in a collapsed, shortened, intussuscepted conformation, and is advanced until it comes to rest in the region of the shortest lesion to be treated. The balloon is then inflated and the lesion treated (i.e. expanded). Following deflation of the balloon, the distal end of the catheter system is moved such that the balloon becomes positioned in the region of the next—shortest lesion to be treated. The effective length of the balloon is then increased by moving the inner conduit in relation to the proximal conduit, following which the balloon is again inflated and the lesion treated. In this way, a series of different length stenoses, in order from the shortest to the longest, may be treated using a single balloon. When used for stent delivery, the stent is pre-loaded into a proximal annular space formed as a result of balloon intususception. The balloon is then moved to the desired site and the stent delivered by means of moving the inner conduit distally (in relation to the outer tube), thereby “unpeeling” the stent from the catheter.
WO 00/38776 discloses a dual-conduit balloon catheter system similar in basic design to that described above in relation to U.S. Pat. No. 6,039,721. This catheter system is intended for use in a vibratory mode in order to break through total occlusions of the vascular lumen. In order to fulfill this aim, the outer conduit has a variable stiffness along its length, while the inner conduit. In addition, the inner conduit while being intrinsically relatively flexible is stiffened by the presence of axial tensioning wires. These conduit design features are used in order to permit optimal translation of vibratory movements of the proximal end of the inner conduit into corresponding vibration of the distal tip thereof.
Rapid exchange (“monorail”) catheters typically comprise a relatively short guide wire lumen provided in a distal section thereof, and a proximal guide wire exit port located between the catheter's distal and proximal ends. This arrangement allows exchange of the catheter over a relatively short guide wire, in a manner which is simple to perform and which can be carried out by a single operator. Rapid exchange catheters have been extensively described in the art, for example, U.S. Pat. Nos. 4,762,129, 4,748,982 and EP0380873.
Rapid exchange catheters are commonly used in Percutaneous Transluminal Coronary Angioplasty (PTCA) procedures, in which obstructed blood vessels are typically dilated by a distal balloon mounted on the catheter's distal end. A stent is often placed at the vessel's dilation zone to prevent reoccurrences of obstruction therein. The dilation balloon is typically inflated via an inflation lumen which extends longitudinally inside the catheter's shaft between the dilation balloon and the catheter's proximal end.
The guide wire lumen passes within a smaller section of the catheter's shaft length and it is accessed via a lateral port situated on the catheter's shaft. This arrangement, wherein the guidewire tube is affixed to the catheter's shaft at the location of its lateral port, usually prevents designers from developing new rapid exchange catheter implementations which requires manipulating its inner shaft. For example, extending or shortening the catheter's length during procedures may be advantageously exploited by physicians to distally extend the length of the catheter into a new site after or during its placement in the patient's artery, for example in order to assist with the passage of tortuous vessels or small diameter stenoses, or to allow in-situ manipulation of an inflated balloon at the distal end of the catheter.
Published International Patent Application, Publication No. WO 2005/102184 discloses a catheter having a rollable expandable element. Published International Patent applications, Publication Nos. WO 2007/004221, WO 2007/042935, WO 2008/004238 and WO 2008/004239, all five published international applications are incorporated herein by reference in their entirety for all purposes, disclose various types of catheters and catheter systems having intususcepting balloon-like inflatable members which may be used, inter alia, to treat plaque by balloon inflation while efficiently collecting plaque debris and other particulate matter from the lumen of pathologically-involved blood vessels and to remove such particles and particulate matter from the blood vessel.
Such inflatable intususceptable balloons may be used to treat plaque by inflating and expanding the balloons after their placement in the plaque region of a blood vessel. Typically, the maximal outer diameter of the balloon in the fully inflated state is limited by the transversal size (or diameter) of the treated blood vessel. Therefore, if one desires to increase the volume available in the intususcepted balloon for including debris particles and plaque particulates within the space formed, one needs to increase the length of the balloon. However, the length of an inflatable balloon having a uniform cross-sectional area will disadvantageously also increase the length of the balloon surface in contact with the blood vessel walls during the fully inflated state of the balloon. Moreover, from the clinical point of view, it is desirable to minimize the length of the balloon portion which would be placed in direct contact with the surface of the blood vessel during the plaque treatment phase (in which the balloon is expanded), as one would like to minimize the possible damage to the blood vessel wall which may be caused by the expansion of the balloon and its contact with the plaque and the associated blood vessel wall.
Thus, there is a need to increase the total volume within the internal space of the balloon in its intussuscepted (invaginated) state, without overly increasing the area of contact of the fully inflated balloon with the walls of the blood vessel during plaque treatment.